Safe use of Thread when processing a request?

[chrisinmtown]

Please advise on proper/safe use of threads in Connexion V3.

Here's the context/requirement. My connexion-based Flask-using REST server accepts a request to interact with a remote system that is slow. My REST server must ack the request immediately, wait for the remote system to finish, then eventually POST back results to a URL supplied in the original request. I don't think this is especially novel or unusual.

I implemented it like this: the function that processes the inbound request starts a Python thread then returns the ack, which I believe finishes the request-response lifecycle. The thread wraps a function that POSTs the data from the request to a remote system, waits for the remote system to answer, then POSTs data back to the caller-supplied URL; then the thread exits.

In the migration guide I saw a warning about use of threads in the context of the new ASGI server, so I figured it might be smart to ask and avoid surprises.

Please comment, thanks in advance.

[RobbeSneyders]

If you are using the AsyncApp, you should be able to use Starlette BackgroundTasks.

With the FlaskApp, I would probably look at a task queue like Celery as explained here, although I have not set this up using Connexion 3 myself.

[chrisinmtown]

Thanks for the really quick reply. Celery looks /waaay/ too heavy for what I need. I found some useful discussion here:

https://stackoverflow.com/questions/76328904/is-there-a-difference-between-starlette-fastapi-background-tasks-and-simply-usin

and that suggested using https://docs.python.org/3/library/asyncio-task.html#asyncio.create_task to create a fire-and-forget IO-bound task, which is exactly what I have here.

Anyhow many people have asked similar questions, I will post a few links:

https://stackoverflow.com/questions/48994440/execute-a-function-after-flask-returns-response
https://stackoverflow.com/questions/60148137/what-happens-if-i-dont-join-a-python-thread

I was just concerned about messing up the Connexion v3, ASGI and uvicorn infrastructure. It doesn't sound like creating a new thread poses any problems for that infrastructure.